1. Field of the Invention
The present invention relates generally to a wireless communication system, and in particular, to an apparatus and method for allocating Channel Quality Information CHannel (CQICH).
2. Description of the Related Art
Wireless access specifications based on a Orthogonal Frequency Division Multiple Access (OFDMA scheme), such as Institute of Electrical and Electronics Engineers (IEEE) 802.16e, IEEE 802.20, and IEEE 802.11n, which is recently under consideration, are taking into account Channel Quality Information (CQI) fed back from a terminal to determine a transmit mode and a transmit rate fit for a channel condition of a scheduled user.
A CQI CHannel (CQICH) is an uplink channel for feeding back the CQI. If a plurality of users utilizes a fixed resource like a data channel, a Base Station (BS) informs the users of resource allocation information of the data channel. Likewise, the BS needs to transmit CQICH resource allocation information to the users. Similar to the resource allocation of the data channel, the CQICH resource allocation information should be transmitted such that every user in a cell can receive the information. To this end, it is important to reduce the amount of the information required for the CQICH allocation.
A current IEEE 802.16e system informs each user of CQICH resource allocation information such as a user IDentification (CQICH_ID), a number of CQICH resources allocated to the corresponding user (CQICH_num), an allocation position (allocation index), an allocation period, and an allocation duration, using separate fields of messages used for the CQICH allocation. For doing so, the current system requires a great deal of downlink broadcast channel resources for the CQICH allocation because the CQICH allocation requires a great deal of information, and the system should inform every user of the information at every CQICH allocation period. As a result, overhead caused by the CQICH allocation is problematic.